U.S. patent application number 12/657079 was filed with the patent office on 2010-05-13 for composite pipe.
Invention is credited to William R. Watson.
Application Number | 20100116373 12/657079 |
Document ID | / |
Family ID | 37448629 |
Filed Date | 2010-05-13 |
United States Patent
Application |
20100116373 |
Kind Code |
A1 |
Watson; William R. |
May 13, 2010 |
Composite Pipe
Abstract
A sleeved composite pipe or piling structure formed of an
elongated polyethylene pipe or tube of high-density polyethylene
(HDPE) or another polyethylene material installed over a
substantially rigid and incompressible hollow metal pipe or solid
wood core having an outer diameter that is the same or slightly
larger than a normal inside diameter of the polyethylene pipe or
tube when measured in a relaxed state at ambient temperature. The
polyethylene pipe or tube is, for example, a HDPE 3408 material
formed of virgin PE 3408 resin as specified in ASTM D3350 with UV
protection, and the pipe is produced to ASTM A-3408. The metal pipe
core can be ferrous or nonferrous pipe.
Inventors: |
Watson; William R.; (Tacoma,
WA) |
Correspondence
Address: |
CHARLES J RUPNICK
PO BOX 46752
SEATTLE
WA
98146
US
|
Family ID: |
37448629 |
Appl. No.: |
12/657079 |
Filed: |
January 13, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11904873 |
Sep 28, 2007 |
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12657079 |
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11132928 |
May 18, 2005 |
7563496 |
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11904873 |
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Current U.S.
Class: |
138/140 |
Current CPC
Class: |
B32B 2250/02 20130101;
B32B 2307/738 20130101; B32B 2250/44 20130101; B32B 2307/51
20130101; B32B 15/085 20130101; B32B 2307/71 20130101; Y10T
428/1393 20150115; B32B 2307/30 20130101; B32B 1/08 20130101; B32B
2307/554 20130101; B32B 2274/00 20130101; B32B 2597/00 20130101;
F16L 9/147 20130101; Y10T 29/49945 20150115; B32B 3/30 20130101;
Y10T 428/1352 20150115; B32B 2307/306 20130101; B32B 15/18
20130101; B32B 2307/714 20130101; B29C 63/18 20130101; B32B 2307/54
20130101; B32B 2307/538 20130101; B32B 27/32 20130101; Y10T
29/49865 20150115 |
Class at
Publication: |
138/140 |
International
Class: |
F16L 9/14 20060101
F16L009/14 |
Claims
1-33. (canceled)
34. A composite structural device, comprising: a substantially
cylindrical rigid core; and an outer peripheral skin in a radially
compressive relationship with the core, the outer peripheral skin
being formed of a sleeve of weldable thermoplastic pipe.
35. The device of claim 34 wherein the sleeve of thermoplastic pipe
further comprises an initial inside diameter that is not larger
than an outside diameter of the core when measured in a relaxed
state prior to being assembled into the radially compressive
relationship with the core.
36. The device of claim 34 wherein the sleeve of thermoplastic pipe
further comprises an initial inside diameter that is smaller than
an outside diameter of the core when measured in a relaxed state
prior to being assembled into the radially compressive relationship
with the core.
37. The device of claim 34 wherein the sleeve of thermoplastic pipe
further comprises an overall length that is less than an overall
length of the core.
38. The device of claim 37, further comprising a nose cone coupled
to the core in a portion thereof exposed by the sleeve of
thermoplastic pipe.
39. The device of claim 34 wherein the core is one of a solid
cylindrical core, and a hollow pipe core.
40. The device of claim 34 wherein the sleeve of weldable
thermoplastic pipe further comprises a length of high pressure
piping material.
41. A composite structural device, comprising: an elongated
substantially cylindrical rigid core; and a sleeve of weldable
thermoplastic pipe assembled over an outside surface of the core,
the pipe having a first relaxed state prior to being assembled over
the outside surface of the core wherein an inside diameter thereof
is smaller than an outside diameter of the core, and a second
assembled state after being circumferentially stretched over the
outside surface of the core wherein an inside diameter thereof is
substantially the same as the outside diameter of the core.
42. The device of claim 41 wherein the assembled state of the
sleeve further comprises the sleeve being in a radially compressive
relationship with the core.
43. The device of claim 41 wherein the cylindrical rigid core
further comprises one of a solid pile and a hollow pipe that is
selected from ferrous pipe and nonferrous pipe.
44. The device of claim 41 wherein an end portion of the core is
exposed beyond the sleeve, and further comprising a metal nose cone
secured to the exposed end portion of the core.
45. A composite structural device, comprising: an elongated core
comprising a substantially straight, rigid and cylindrical section;
an elongated tubular sleeve comprising a weldable thermoplastic
material and having an inside diameter as measured in a relaxed
state that is the same or less than an outside diameter of the
core; a longitudinal axis of the tubular sleeve being substantially
aligned with a longitudinal axis of the core; and the sleeve being
installed over at least a portion of the core, and the inside
diameter of the sleeve being simultaneously expanded to
substantially match the outside diameter of the core.
46. The device of claim 45 wherein the weldable thermoplastic of
the tubular sleeve further comprises a weldable thermoplastic
material that is radially expandable without tearing.
47. The device of claim 45 wherein the core further comprises one
of a solid pile and a hollow pipe, the hollow pipe being one of a
ferrous pipe and a nonferrous pipe.
48. The device of claim 47 wherein the lubricant further comprises
a material that is substantially chemically inert relative to each
of the core and the sleeve.
49. The device of claim 48 wherein the weldable thermoplastic
material further comprises high-density polyethylene (HDPE) high
pressure piping material.
50. The device of claim 49, further comprising an end portion of
the core being exposed beyond the sleeve; and a metal nose cone
secured to the exposed end portion of the core.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a composite pipe device,
and in particular to a sleeve of high-density polyethylene (HDPE)
pipe compression fit over a metal pipe or solid core.
BACKGROUND OF THE INVENTION
[0002] Corrosion has always been a problem for metal pipe,
especially those buried underground or driven into the sea floor
for use as pilings. Even galvanized pipe corrodes over time as the
thin galvanic coating wears away. Different composite pipe devices
are also known, including pipe devices having a plastic shell
extruded over the pipe. However, known plastic-metal composite pipe
is formed of recycled material extruded over pipe of undetermined
structural quality, which results in an composite pipe of unknown
quality that requires further testing and certification for use in
many industrial applications.
SUMMARY OF THE INVENTION
[0003] The present invention overcomes the manufacturing and load
capacity limitations of the prior art by providing a sleeved or
"jacketed" composite pipe structure formed of an elongated
polyethylene pipe or tube of high-density polyethylene (HDPE) or
another polyethylene material installed over a substantially rigid
and incompressible steel or other metal pipe core having an outer
diameter that is the same or slightly larger than a normal inside
diameter of the polyethylene pipe or tube when measured in a
relaxed state at ambient temperature. The polyethylene pipe or tube
is, for example, a HDPE 3408 material formed of virgin PE 3408
resin as specified in ASTM D3350 with UV protection, and the pipe
is produced to ASTM A-3408. The metal pipe core can be ferrous or
nonferrous pipe.
[0004] According to one aspect of the invention, the wherein the
elongated polyethylene pipe or tube is pre-heated to expand its
inside diameter and soften the material. The elongated polyethylene
pipe or tube is slid, possibly under some axial force or pressure,
over the piling or pipe. Sliding the elongated polyethylene pipe or
tube over the larger diameter core further expands its inside
diameter to larger than its relaxed state measurement. After
installation over the core, the elongated polyethylene pipe or tube
is permitted to relax and contract or "shrink" radially, whereby
the polyethylene pipe or tube radially compresses the outside of
the substantially rigid and incompressible core pipe. When
pre-heated, the inside diameter of the polyethylene pipe or tube
contract or shrinks radially upon cooling to form a compression fit
around the rigid core.
[0005] According to one aspect of the invention, the core is
alternatively a wooden post for use as a pile.
[0006] According to another aspect of the invention, when the wood
piling or steel pipe is to be used as a piling, the polyethylene
pipe or tube is extended to or past the ends of the core pipe, and
the open ends of the polyethylene pipe or tube are closed by
plastic caps that are thermal fusion plastic welded or chemically
welded in a water-tight manner. When the steel pipe is to be used
in a string to form a pipe line, the steel pipe is extended beyond
the polyethylene pipe or tube to expose short length of the core
pipes, adjacent pipes are steel welded or otherwise joined, and
"clamshell" portions of polyethylene material is chemically or
thermal fusion welded between the polyethylene pipe or tube of
adjacent pipes in a water-tight manner.
[0007] Other aspects of the invention are detailed herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The foregoing aspects and many of the attendant advantages
of this invention will become more readily appreciated as the same
becomes better understood by reference to the following detailed
description, when taken in conjunction with the accompanying
drawings, wherein:
[0009] FIG. 1 is an end view that illustrates the present invention
by example and without limitation embodied as a composite
structural device formed of an elongated substantially cylindrical
hollow pipe core material having an outer peripheral skin formed of
a sleeve of seamless extruded or seam welded plastic pipe that is
adhered to the core material by friction caused by radial
compression;
[0010] FIG. 2 is an end view that illustrates the composite
structural device of the present invention wherein the elongated
substantially cylindrical core is a solid core, such as a solid
wooden or plastic pile;
[0011] FIG. 3 is a flow diagram that illustrates the process of the
invention whereby the composite structural device of the present
invention is formed;
[0012] FIG. 4 illustrates the mechanical process of the invention
prior to assembly of the core and plastic pipe sleeve;
[0013] FIG. 5 illustrates one embodiment of the invention at an
intermediate stage of assembly of the core and plastic pipe
sleeve;
[0014] FIG. 6 illustrates an alternative embodiment of the
invention at an intermediate stage of assembly of the core and
plastic pipe sleeve;
[0015] FIG. 7 illustrates one embodiment of the invention at an end
stage of assembly of the core and plastic pipe sleeve;
[0016] FIG. 8 illustrates an embodiment of the invention wherein
two or more composite devices of the invention are joined by
lengthwise joints into a longer string of such devices;
[0017] FIG. 9 illustrates one embodiment of the invention wherein a
metal nose cone is provided in the exposed portion of the core to
operate as a means for protecting and sealing the annular joint
developed at the interface between the core and plastic pipe sleeve
when the composite structural device is driven lengthwise into the
earth or another medium;
[0018] FIG. 10 illustrates the nose cone of the invention
illustrated in FIG. 9 being collapsed about a portion of the
exposed portion of the core and extending over a lip portion of the
plastic pipe sleeve plastic pipe sleeve, whereby the nose cone
protects the entrance to an annular joint at the interface between
the core and plastic pipe sleeve;
[0019] FIG. 11 illustrates one embodiment of the invention that is
useful for the composite structural device being used as a piling
wherein a quantity of supplemental rub strips are welded to the
outer wall surface of the plastic pipe sleeve as a means for
protecting the integrity of the plastic pipe sleeve in high wear
applications; and
[0020] FIG. 12 illustrates another embodiment of the invention that
is useful for the composite structural device being used as a
piling wherein a traveler is provided over the outer wall surface
of the plastic pipe sleeve as a means for protecting the integrity
of the plastic pipe sleeve in high wear applications.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
[0021] In the Figures, like numerals indicate like elements.
[0022] FIG. 1 is an end view that illustrates the present invention
by example and without limitation embodied as a composite
structural device formed of an elongated substantially cylindrical
hollow pipe core material having an outer peripheral skin formed of
a sleeve of seamless extruded or seam welded plastic pipe that is
adhered to the core material by friction caused by radial
compression.
[0023] As illustrated in FIG. 1, the composite structural device 10
of the invention is formed of an elongated substantially
cylindrical metal pipe core 12 having an outer peripheral skin
formed of a sleeve of seamless extruded or seam welded plastic pipe
14. The plastic pipe sleeve 14 is adhered to the metal pipe core 12
by intersurface friction caused by radial compression that results
from the plastic pipe sleeve 14 having a nominal inside diameter
ID.sub.p before installation that is the substantially same or
smaller than an outside diameter OD.sub.c of the metal pipe core
12, and a "memory" or tendency to return or "shrink" to its nominal
inside diameter ID.sub.p, after installation.
[0024] According to one embodiment of the invention, the metal pipe
core 12 is a ferrous material, such as any grade of carbon or
stainless steel, ductile iron, a nickel-based ferrous material such
as Inconel.RTM. which refers to a family of trademarked high
strength austenitic nickel-chromium-iron (NiCrFe) alloys that
contain high levels of nickel and can be thought of as
super-stainless steels having exceptional anti-corrosion and
heat-resistance properties for use in a variety of extreme
applications including navy boat exhaust ducts, submarine
propulsion motors, undersea cable sheathing, heat exchanger tubing
and gas turbine shroud rings, as well as other ferrous materials.
According to other embodiments of the invention, the metal pipe
core 12 is a nonferrous material, such any grade of aluminum or
aluminum alloy.
[0025] According to one embodiment of the invention, the plastic
pipe sleeve 14 is formed of a thermoplastic material that is
weldable in a water-tight manner by means of thermal fusion plastic
welding or chemical welding (hereinafter "plastic welding"). For
example, according to one embodiment of the invention, the plastic
pipe sleeve 14 is pressure-rated thermoplastic pipe, such as
polyethylene pipe (PE) including high-density polyethylene (HDPE),
ultrahigh molecular weight (UHMW) PE and cross-linked PE plastic
piping materials. Such thermoplastic materials are widely used
because of their chemical resistance, freeze resistance, impact and
abrasion resistance, stress absorption properties, and weathering
capabilities including resistance to sunlight and ultraviolet (UV)
attack, but also because of their low cost and, because these
materials are chemically inert, they are even approved for use
around fish and plants. These thermoplastic pipe materials are
commercially available in low, medium and high density (Type II and
Type III). Their low cost is due in part to their fabrication which
is usually by extrusion of seamless pipe, but may be by rolled
sheets with heat-fused joints that result in an exceptionally
smooth inner surface within the pipe.
[0026] Ultrahigh molecular weight (UHMW) PE and cross-linked PE
plastic piping materials are a relatively new developments in PE
piping. The UHMW PE has considerably higher resistance to
stress-cracking but is more costly than conventional PE piping
material. It offers an extra margin of safety when used in
sustained pressure conditions in comparison with pipe made from
lower molecular weight resin. It is suitable for certain
applications in the chemical industry where stress-cracking
resistance has been a limiting factor for the conventional PE
pipe.
[0027] Cross-linked PE piping material, when compared to ordinary
PE pipe, displays greater strength, higher stiffness and improved
resistance to abrasion and to most chemicals and solvents at
elevated temperatures up to 95 degrees C. (203 degrees F.). Pipe
made from cross-linked PE also has high-impact resistance even at
sub-zero temperatures. It is used in applications too severe for
ordinary PE pipe and is strong enough for joining by threading.
[0028] High-density polyethylene (HDPE) piping material is made
from a crystalline resin or polymer known for its flexibility,
toughness and chemical resistance. These features make HDPE
pressure pipe well suited for those applications or industries
requiring a pipe that is strong, durable, corrosion resistant and
yet at the same time flexible enough to be assembled and installed
in the most inaccessible and harsh environments. HDPE pressure pipe
is the preferred pipe of choice for most trenchless technologies
like pipe bursting and horizontal direction drilling. HDPE pressure
pipe is a common choice for projects requiring a piping solution
that must be able to cope with extreme pressure loads under harsh
conditions.
[0029] HDPE 3408 is one example of high-density polyethylene (HDPE)
high pressure piping material. HDPE 3408 is a premium quality, high
density, extra high molecular weight (EHMW) black polyethylene pipe
that is specifically intended for the rigors of the oil field. It
is produced from virgin PE 3408 resin as specified in ASTM D3350
and contains carbon black for superior resistance to UV
degradation. HDPE 3408 pipe is manufactured in accordance with the
ASTM A-3408 standard, as well as AWWA, ASTM, FM, CSA, BNQ, and NSF
Standards. HDPE 3408 pipe offers outstanding environmental stress
crack resistance, the highest chemical resistance of any
polyethylene pipe and high impact resistance, and is made tough
enough to easily handle pressure fluctuation and line surges. HDPE
3408 pipe diameters are known to range from 1/2 inch to 6 inch
coiled, and 1/2 inch to at least 54 inch straight lengths.
[0030] HDPE 3408 black polyethylene pipe is manufactured to
withstand extended outdoor storage and above-ground use in most
climates by dispersion of fine carbon black which is the most
effective additive for protecting polyethylene from the effects of
weathering. By example and without limitation, one commercially
available brand of HDPE 3408 black polyethylene pipe includes a
minimum of 2 percent finely dispersed carbon black. Such
UV-stabilized HDPE pipe can be exposed for long periods of time
without decline in performance level. Weathering capabilities of
HDPE pipe also include freeze resistance.
[0031] The virgin PE 3408 is a microbiological resistant
polyethylene resin that offers optimum chemical resistance so that
pipe made of HDPE PE-3408 easily withstands high acid soils and
fertilizers and is capable of handling the transfer of extremely
corrosive materials, e.g., industrial wastes and chemical acids.
Because HDPE is resistant to a broad range of chemicals in varying
degrees of concentration, sunlight and UV attack, as well as being
approved for use with fish and plants, it is known as an excellent
application for leach pads, wastewater ponds, landfills,
aquaculture systems, landfill covers, secondary containment and
tanks.
[0032] HDPE PE 3408 pressure pipe is manufactured from a high
density polyethylene polymer of a molecular structure having much
longer chains with fewer side branching when compared to ordinary
polyethylene piping material so that HDPE PE 3408 pressure pipe has
greater density and a crystallinity level in the range of 85
percent. As a rule, when the density increases, the stiffness,
harness, strength, heat distortion point, and ability to transmit
gasses increases. When density decreases, impact strength and
stress crack resistance increases, where stress cracking is a
surface change that polyethylene undergoes when exposed to oils,
gasoline and other hydrocarbons. HDPE PE 3408 pressure pipe is
rated at a density range of 0.941 to 0.965 gr/cc and is therefore
superior in stiffness, hardness and strength which causes it to be
ideal for pressure applications. Most importantly, HDPE PE 3408
pressure pipe can handle greater pressures under extremely
corrosive conditions. For example, HDPE PE 3408 pressure pipe can
be buried to great depths and can tolerate severe soil strain and
soil movements (rise or settlement), and is even seismically
qualified in laboratory studies and field proven to be earthquake
tolerant.
[0033] Table 1 illustrates typical physical properties of high
density polyethylene pipe, as provided by Chevron Phillips Chemical
Company. This list of typical physical properties shown in Table 1
is intended for basic characterization of the material and does not
represent specific determinations of specifications. The physical
properties values reported in Table 1 were determined on
compression molded specimens prepared in accordance with Procedure
C of ASTM D 1928 and may differ from specimens taken from pipe. In
some instances, testing may have been discontinued because no
failures and no indication of stress crack initiation occurred.
TABLE-US-00001 TABLE 1 Property Specification Unit Nominal Value
Material Designation PPI/ASTM PE 3408 Material Classification ASTM
D-1248 III C 5 P34 Cell Classification ASTM D3350-99 345464C
-Density (3) ASTM D-1505 gm/cm3 0.955 -Melt Index (4) ASTM D-1238
gm/10 min. 0.11* (216 kg/190 C.) -Flex Modulus (5) ASTM D-790 psi
135,000 -Tensile Strength (4) ASTM D-638 psi 3,200 PENT (6) ASTM
F-1473 Hours >100 -HDB @73.sub.i F (4) ASTM D-2837 psi 1,600
-HDB @ 140 Deg F ASTM D-2837 psi 800 -U-V Stabilizer (C) ASTM
D-1603 % C 2.5 Hardness ASTM D-2240 Shore "D" 65 Compressive
Strength (yield) ASTM D-695 psi 1,600 Tensile Strength @ Yield ASTM
D-638 (2''/min.) psi 3,200 (Type IV Spec.) Elongation @ Yield ASTM
D-638 %, minimum 8 Tensile Strength @ Break ASTM D-638 psi 5,000
(Type IV Spec.) Elongation @ Break ASTM D-638 %, minimum 750
Modulus of Elasticity ASTM D-638 psi 130,000 PENT (6) ASTM F-1473
Hours >100 (Cond. A, B, C: Mold. Slab) ASTM D-1693 Fo, Hours
>5,000 (Compressed Ring-pipe) ASTM F-1248 Fo, Hours >3,500
Slow Crack Growth Battelle Method Days to Failure >64 Impact
Strength (IZOD) ASTM D-256 In-lb/in notch 42 (.125O Thick) (Method
A) Linear Coefficient of Thermal ASTM D-696 in/in/F. 1.2 .times.
10-4 Expansion Thermal Conductivity ASTM D-177 BTU-in/ft.sup.2/hrs/
2.7 degrees F. Brittleness Temp. ASTM D-746 degrees F. <-180
Vicat Soft. Temp. ASTM D-1525 degrees F. 257 Heat Fusion Cond. ASTM
D-1525 @ psi degrees F. 75 @ 400 *Average Melt Index value with a
standard deviation of 0.01
[0034] Medium density polyethylene is an alternative piping
material for the plastic pipe sleeve 14 of the invention. According
to one embodiment of the invention, a minimum carbon black content
of 2.5 percent provides excellent protection from UV rays and harsh
weather conditions. Medium Density Polyethylene has a 20 year
average life and puncture and tear strengths that far exceed common
polyethylene or vinyl films. Medium Density Polyethylene is
commonly used for larger ponds, including lagoons, canal liners,
fire ponds, remediation liners, cargo covers, oil field pit liners,
silage covers, outdoor covers, brine ponds, mine trailing ponds,
interim landfill caps, leachate collection ponds.
[0035] Polyethylene piping material is quickly and easily joined
and installed by using the heat fusion method which produces a
solid, leak-proof joint that is as strong as the base pipe.
[0036] While the molecular structure of HDPE pipe gives it certain
advantages over other plastic pipe for the plastic pipe sleeve 14
of the invention, the only absolute requirement of the invention is
the plastic pipe sleeve 14 must expand radially to admit the core
12 thereinto, and thereafter radially contract to bring an inner
wall surface IW.sub.p of the plastic pipe sleeve 14 into a
compressive contact with an outer wall surface OW.sub.c of the core
12. Accordingly, different plastic pipes are alternatively
substituted for the HDPE pipe, HDPE PE 3408 pressure pipe, UHMW PE
pipe, medium density polyethylene pipe, cross-linked PE pipe or
other polyethylene piping materials described herein.
[0037] According to one embodiment of the invention, the plastic
pipe sleeve 14 is a acrylonitrile-butadiene-styrene (ABS) pipe,
which is a copolymer made from the three monomers described in the
heading, and contains at least 15 percent of acrylonitrile. ABS is
a rigid plastic with good impact resistance at lower temperatures
down to -40 degrees C. (-40 degrees F.) and can be used at
temperatures up to 80 degrees C. (176 degrees F.). ABS is utilized
mainly for drain-waste-ventilation (DWV) pipe and fittings but it
is also used in solvent cement for installing pipe in various
applications. ABS pipe can be joined by solvent welding or
threading. A new development in the ABS-DWV piping industry is the
co-extruded foam-core ABS pipe that is also useful for practicing
the invention. ABS-DWV has a foam core sandwiched between solid
skins and is useful as sewer, conduit and duct pipe. The foam-core
ABS-DWV pipe has lower resin requirements than conventional ABS
pipe.
[0038] According to another embodiment of the invention, the
plastic pipe sleeve 14 is a polybutylene (PB) pipe, which has
practically no creep and has excellent resistance to stress
cracking. Polybutylene plastic pipe is flexible, and in many
respects similar to Type III polyethylene, but is stronger.
Polybutylene plastic piping is relatively new, and thus far its use
has been limited to the conveyance of natural gas and to water
distribution systems. High temperature grade polybutylene plastic
pipe can resist temperatures of 105 to 110 degrees C. (221 to 230
degrees F.).
[0039] According to another embodiment of the invention, the
plastic pipe sleeve 14 is a polypropylene (PP) piping, which is the
lightest-weight plastic material, having a density of 0.90
g/cm.sup.3, and generally has better chemical resistance than other
plastics. Polypropylene is used in some pressure piping
applications, but its primary use is in low pressure lines.
Polypropylene plastic pipe is used for chemical (usually acid)
waste drainage systems, natural-gas and oil-field systems, and
water lines. The maximum temperature for non-pressure polypropylene
piping is 90 degrees C. (194 degrees F.). Pipe lengths are joined
by heat fusion, threading, e.g., with heavy pipe, and mechanical
seal devices.
[0040] According to other embodiments of the invention, the plastic
pipe sleeve 14 is another thermoplastic used in the manufacture of
pipe, including poly(vinylidene chloride), poly(vinylidene
fluoride), cellulose acetate butyrate (CAB), acetal homopolymer
resins, rubber-modified systems, polytetrafluoroethylene (PTFE),
and fluorinated ethylene-propylene (FEP) copolymer. However, these
materials are relatively more expensive.
[0041] When the plastic pipe sleeve 14 is practiced using one of
the thermoplastic piping options, such as polyethylene and in
particular HDPE PE 3408 pressure pipe, sleeves 14 of two composite
pilings 10 are easily fusion welded together with weld joints as
strong as the original pipe whereby the thermoplastic piping is a
monolithic or one piece piping solution. This monolithic
thermoplastic piping solution is ideal for corrosive applications
compared to other piping materials such as galvanized steel pipe
which can wear through in time making them susceptible to possible
leaks or pressure failure. Secondly, when the plastic pipe sleeve
14 is practiced using one of the thermoplastic piping options
manufactured in accordance with the ASTM A-3408 standard or another
accepted standard using virgin PE 3408 resin material in accordance
with the ASTM D3350 standard or another virgin resin material in
accordance with another accepted standard, and the metal pipe core
12 is manufactured in accordance with an accepted standard, the
composite structural device 10 of the invention is fully compliant
with accepted ASTM standards without further testing or
certification.
[0042] FIG. 2 is an end view that illustrates the composite
structural device 10 of the present invention wherein the elongated
substantially cylindrical core 12 is a solid core, such as a solid
wooden or plastic pile in contrast to the metal pipe core
illustrated in FIG. 1. The solid core 12 is an elongated
substantially cylindrical core having an outer peripheral skin
formed of the sleeve 14 of seamless extruded or seam welded plastic
pipe that is adhered to the core material by friction caused by
radial compression.
[0043] FIG. 3 is a flow diagram that illustrates the process of the
invention whereby the composite structural device 10 of the present
invention is formed.
[0044] FIGS. 4, 5, 6 and 7 are pictorial views that illustrate the
mechanical process of the invention as illustrated in FIG. 3,
whereby the composite structural device 10 of the present invention
is formed. FIG. 4 illustrates the mechanical process of the
invention prior to assembly of the core 12 and plastic pipe sleeve
14. FIG. 5 illustrates one embodiment of the invention at an
intermediate stage of assembly of the core 12 and plastic pipe
sleeve 14. FIG. 6 illustrates an alternative embodiment of the
invention at an intermediate stage of assembly of the core 12 and
plastic pipe sleeve 14.
[0045] In step A of the invention, an elongated substantially
cylindrical core 12 is selected. The core 12 may be either a solid
core of the type illustrated in FIG. 2, or a tubular pipe core of
the type illustrated in FIG. 1. If the core 12 is a hollow pipe, it
may be selected from any form or grade of ferrous or nonferrous
pipe material manufactured according to an accepted ASTM standard,
as discussed herein, and from any length appropriate to the
end-user application. When an inner diameter of the end product is
a desirable result, the pipe core 12 is selected having an inner
diameter ID.sub.c of the desired dimension formed by an inner wall
surface IW.sub.c.
[0046] In step B of the invention, a plastic pipe sleeve 14 is
selected from any plastic tube or pipe material that is radially
expandable without tearing. According to one embodiment of the
invention, the core 12 is selected from the family of HDPE piping
materials. According to one embodiment of the invention, the
plastic pipe sleeve 14 is a pipe is produced in accordance with
ASTM A-3408 using HDPE 3408 material formed of virgin PE 3408 resin
as specified in ASTM D3350 and contains carbon black for UV
protection. The plastic pipe sleeve 14 is selected having a nominal
inside diameter ID.sub.p before installation that is the same or
slightly smaller than an outside diameter OD.sub.c of the selected
core 12.
[0047] When the plastic pipe sleeve 14 is produced by extrusion,
the inner wall surface IW.sub.p is sufficiently smooth to accept
the core 12 with little or no drag. When the plastic pipe sleeve 14
is a pipe is produced in accordance with ASTM A-3408, it has an
exceptionally smooth inner surface, and any heat-fused joints offer
little drag or resistance within the pipe to acceptance of the core
12. Accordingly, a longitudinal force F.sub.L applied during
installation of the plastic pipe sleeve 14 onto the steel pipe or
other elongated substantially cylindrical core 12 is minimized.
[0048] Alternatively, if an outer diameter of the end product is a
desirable result, the plastic pipe sleeve 14 is selected having an
outer diameter OD.sub.p that, in a relaxed state prior to
installation over the core 12, is the same or smaller than the
desired outer diameter result, and the core 12 is selected having
an outer diameter OD.sub.c that is the same or slightly larger than
a normal inside diameter ID.sub.p of the plastic pipe sleeve
14.
[0049] Accordingly to one embodiment of the process of the
invention, in a step C the plastic pipe sleeve 14 is optionally
pre-warmed to a temperature above ambient but below a melting point
of the sleeve material, e.g. below 240 degrees F. when the plastic
pipe sleeve 14 is formed of HDPE PE 3408 pipe. Pre-warming the
plastic pipe sleeve 14 is optional, but such pre-warming reduces
the force F.sub.L applied during installation of the plastic pipe
sleeve 14 onto the steel pipe or other elongated substantially
cylindrical core 12, as discussed herein. Selection of pre-warming,
and if present, pre-warming temperature is also a function of the
"stretchability" of the plastic pipe sleeve 14. All relevant
dimensions being equal, a plastic pipe sleeve 14 of a more
stretchable material is more easily installed over a core 12 than a
plastic pipe sleeve 14 of a less stretchable material. Thus, a
plastic pipe sleeve 14 of a less stretchable material is optionally
pre-warmed to a higher temperature than a plastic pipe sleeve 14 of
a more stretchable material to reduce the force F.sub.L applied
during installation of the plastic pipe sleeve 14 onto the core
12.
[0050] If present, pre-warming of the plastic pipe sleeve 14 may be
practiced using any means available. For example, pre-warming of
the plastic pipe sleeve 14 is practiced by immersion for a period
of time in a liquid such as oil or water heated to a temperature
above ambient but below a melting point of the sleeve material, or
immersion in a similarly heated environment such as a steam bath.
Pre-warming of the plastic pipe sleeve 14 is alternatively
practiced by open flame, as produced by a gas-fired torch, or
radiant heat from a bed of hot coals, as long as the plastic pipe
sleeve 14 is not warmed above the melting point of the sleeve
material. Pre-warming is alternatively practiced by allowing the
plastic pipe sleeve 14 to stand or lie in a natural warming
environment, for example, out doors in warm weather or under the
direct rays of the sun. According to one embodiment of the
invention, pre-warming is practiced by installing the plastic pipe
sleeve 14 in an oven or other warming device 16 (hereinafter
warming device 16) sized to accommodate the selected length L.sub.p
of the section of plastic pipe sleeve 14 to be installed on the
elongated core 12, which may be the same or less than the overall
length L.sub.c of the elongated core 12. The warming device 16 is,
for example, a tubular propane-fired oven, a natural gas or other
gas-fired oven, an electric current oven such as an induction, arc
or resistance oven, or an oven operated with a different heat
source. The warming device 16 or other pre-warming means does not
even have to heat the entire plastic pipe sleeve 14 to a uniform
temperature throughout. Rather, one side can be pre-warmed to a
much higher temperature than an opposite side, as in sun warming of
a plastic pipe sleeve 14 lying on the ground. The invention may be
practiced using nonuniform pre-warming at least, first, because
pre-warming of the plastic pipe sleeve 14 is not a requirement of
the installation process, second, because partial pre-warming is
effective for softening and making more pliable at least that
portion of the plastic pipe sleeve 14 that is so pre-warmed, third,
because heat conduction through the material tends to equalize the
temperature throughout the plastic pipe sleeve 14.
[0051] According to one embodiment of the invention, when the
plastic pipe sleeve 14 is high-density polyethylene (HDPE) pipe,
the plastic pipe sleeve 14 is pre-warmed to about 150 degrees F.
which is above ambient but well below a melting point of the HDPE
sleeve material.
[0052] In an optional step D of the invention, a lubricant 18 is
applied to the inner wall surface IW.sub.p of the plastic pipe
sleeve 14, either before or after pre-warming. The lubricant 18
operates as a means for overcoming frictional forces between the
core 12 and plastic pipe sleeve 14 as a further optional means for
minimizing or at least reducing the force F.sub.L applied during
installation of the plastic pipe sleeve 14 onto the steel pipe or
other elongated substantially cylindrical core 12, as discussed
herein. The lubricant 18 is selected to avoid chemical interaction
with either the material of the core 12 or the material of the
plastic pipe sleeve 14. For example, if the plastic pipe sleeve 14
is selected to be HDPE pipe, carbon or petroleum based products are
avoided for use as the lubricant 18 because such products are known
to attack the cellular matrix of polyethylene piping materials and
to cause softening of the materials over time, whereby the plastic
pipe sleeve 14 tends to loose its pressure rating and rupture under
load. According to one embodiment of the invention, the lubricant
is instead selected to be a light vegetable oil.
[0053] According to one embodiment of the invention wherein the
lubricant 18 is a light vegetable oil applied to the inside wall
surface IW.sub.p of the plastic pipe sleeve 14, the plastic pipe
sleeve 14 is pre-warmed to a temperature that is at least slightly
below the cook-off temperature of the vegetable oil of about 160
degrees F. Accordingly, the plastic pipe sleeve 14 is pre-warmed to
about 150 degrees F. which is well above ambient but still slightly
below the cook-off temperature of the vegetable oil lubricant
18.
[0054] According to one alternative embodiment of the process of
the invention illustrated in FIG. 3, the lubricant 18 is optionally
applied to an outer wall surface OW.sub.c of the core 12, either
instead or in combination with the lubricant 18 that is applied to
the inner wall surface IW.sub.p of the plastic pipe sleeve 14 in
optional step D of the invention. As described above, the lubricant
18 operates as a means for overcoming frictional forces between the
core 12 and plastic pipe sleeve 14 as a further optional means for
reducing the force F.sub.L applied during installation of the
plastic pipe sleeve 14 onto the steel pipe or other elongated core
12, as discussed herein. As is further discussed herein, the
lubricant 18 is selected to avoid chemical interaction with either
the material of the core 12 or the material of the plastic pipe
sleeve 14.
[0055] According to another alternative embodiment of the process
of the invention illustrated in FIG. 3, the lubricant 18 is
optionally applied to the outer wall surface OW.sub.c of the core
12 during installation of the plastic pipe sleeve 14. Accordingly,
the lubricant 18 is applied to the outer wall surface OW.sub.c of
the core 12 as or immediately before entry into the plastic pipe
sleeve 14 by means of a lubricant dispenser 19 provided adjacent to
where the core 12 meets the plastic pipe sleeve 14.
[0056] Preferably, the core 12 is not pre-warmed so that any
thermal expansion due to such pre-warming is avoided.
[0057] In step E of the invention, a first open end or mouth 20 of
the plastic pipe sleeve 14 is exposed. If the plastic pipe sleeve
14 is pre-warmed in a warming device 16 of a type having doors 22,
the mouth 20 of the plastic pipe sleeve 14 is positioned in the
warming device 16 such that, when the doors 22 are opened, the
mouth 20 is exposed and available for installation over the core
12. According to one embodiment of the invention, the plastic pipe
sleeve 14 optionally remains in the warming device 16 or other
warming device as a means for retaining the temperature to which it
has been pre-warmed. Alternatively, the plastic pipe sleeve 14 is
removed from the warming device 16 prior to installation over the
core 12.
[0058] In step F of the invention, a longitudinal axis A.sub.c of
the core 12 is initially aligned with a longitudinal axis A.sub.p
of the plastic pipe sleeve 14, whether the plastic pipe sleeve 14
remains in the warming device 16, or is removed previously
therefrom. For example, the core 12 and plastic pipe sleeve 14 are
both supported on a linear array of substantially horizontal
rollers R.sub.H that extends continuously from a distance in front
of the oven door 20 up to and through the oven door 20 into the
oven or other warming device 16 and extends substantially to a back
wall 24 of the warming device 16 opposite the door 20, whereby the
outer wall surface OW.sub.c of the elongated core 12 and an outer
wall surface OW.sub.p of the plastic pipe sleeve 14 are supported
on a plane P defined by an operational surface of the horizontal
rollers R.sub.H with the plastic pipe sleeve 14 installed in the
warming device 16 where it is pre-warmed to the selected
temperature, and with the elongated core 12 positioned outside the
warming device 16 before the door 20. Linear arrays of rollers
R.sub.H for such support are well-known in the pipe manufacturing
arts as well as other material movement arts and are generally
commercially available. Some commercially available systems of
rollers R include two side-by-side linear arrays of rollers R with
a second array being inclined relative to a first array such as to
form an angle or "V" there between, whereby the core 12 and plastic
pipe sleeve 14 are forced into mutual axial alignment.
Alternatively, a block or stop is provided on one side of the array
of horizontal rollers R.sub.H as a guide for aligning the core 12
and plastic pipe sleeve 14. According to one embodiment of the
invention, a linear array of vertical rollers R.sub.V is provided
beside the linear array of horizontal rollers R.sub.H to operate as
a means for substantially horizontally aligning the longitudinal
axes A.sub.c and A.sub.p of the core 12 and plastic pipe sleeve 14,
while the linear array of horizontal rollers R.sub.H operates as a
means for substantially vertically aligning the respective core and
sleeve longitudinal axes A.sub.c and A.sub.p.
[0059] Optionally, means are provided for radially supporting the
pre-warmed plastic pipe sleeve 14 against buckling under the
longitudinal insertion force F.sub.L applied during installation of
the plastic pipe sleeve 14 onto the core 12. According to one
embodiment of the invention, one or more additional rollers R.sub.A
are provided in different positions around the outer periphery of
the plastic pipe sleeve 14 as a means for radially supporting the
pre-warmed plastic pipe sleeve 14. Alternatively, the physical
constraints of one or more interior oven walls 26 operate as a
means for radially supporting the pre-warmed plastic pipe sleeve
14.
[0060] Furthermore, a second end or foot 28 of the plastic pipe
sleeve 14 is supported against longitudinal movement in a direction
opposite the sleeve mouth 20. In other words, the foot 28 of the
plastic pipe sleeve 14 is supported against being pushed away when
the longitudinal force F.sub.L applied during installation of the
plastic pipe sleeve 14 onto the core 12. For example, the foot 28
is positioned adjacent or proximate or even in actual butted
contact with a block or other stop 30 located intermediate the oven
door 22 and the back wall 24 of the warming device 16. Stop 30 is
useful when the plastic pipe sleeve 14 is short as compared with
the oven length between the door 22 and back wall 24. Stop 30 is
also useful when the core 12 is intended to extend beyond the foot
28 of the plastic pipe sleeve 14, as discussed herein.
Alternatively, the foot 28 of the plastic pipe sleeve 14 is
positioned adjacent or proximate or even in actual butted contact
with the back wall 24 of the warming device 16, whereby the back
wall 24 operates as the stop 30. Accordingly, the core 12 and
plastic pipe sleeve 14 are relatively aligned and positioned for
insertion of the plastic pipe sleeve 14 over the core 12.
[0061] In step G of the invention, a first end or nose 32 of the
core 12 is applied to the first end or mouth 20 of the plastic pipe
sleeve 14 and the respective longitudinal axes A.sub.c and A.sub.p
of the core 12 and plastic pipe sleeve 14 are accurately aligned.
Optionally, either one or both of the core nose 32 and the sleeve
mouth 20 is provided with a lead-in that operates as a means for
more accurately aligning the respective longitudinal axes A.sub.c
and A.sub.p of the core 12 and plastic pipe sleeve 14 than is
provided by the manufacturing equipment during the initial
alignment. The core 12 and plastic pipe sleeve 14 may have
different respective outside diameters OD.sub.c and OD.sub.p
depending upon such factors as the wall thickness of the plastic
pipe sleeve 14 and degree of interference fit, i.e., radial
compression, desired between the core 12 and plastic pipe sleeve
14. Therefore, the respective longitudinal axes A.sub.c and A.sub.p
of the core 12 and plastic pipe sleeve 14 may be substantially but
not accurately aligned by the horizontal rollers R.sub.H and
vertical rollers R.sub.V, if present. Also equipment tolerances and
other vagaries common to manufacturing facilities may tend to
slightly misalign the respective longitudinal axes A.sub.c and
A.sub.p of the core 12 and plastic pipe sleeve 14. Therefore,
according to one embodiment of the invention, when the core 12 is a
pipe manufactured according to an accepted ASTM standard, as
discussed herein, the nose 32 is normally provided with a 33 degree
bevel nominally used in butt welding pipe. This bevel operates as a
lead-in 34 for accurately aligning the respective longitudinal axes
A.sub.c and A.sub.p of the core 12 and plastic pipe sleeve 14 and
thereafter guiding the nose 32 of the core 12 into the interior of
the plastic pipe sleeve 14. Stated differently, the lead-in 34 on
the nose 32 operates to align the longitudinal axis A.sub.p of the
plastic pipe sleeve 14 with the longitudinal axis A.sub.c of the
core 12 and further to guide the plastic pipe sleeve 14 onto the
core 12. When the core 12 is a solid core of the type illustrated
in FIG. 2, the lead-in 34 is optionally cut on the nose 32.
Alternatively, a lead-in 36 is provided on the plastic pipe sleeve
14 as an internal bevel around the mouth 20. The angle and depth of
the respective lead-ins 34, 36 is selected as a function of several
factors, including: the relative outside diameter OD.sub.c of the
core 12; the inside diameter ID.sub.p of the plastic pipe sleeve
14; the sleeve wall thickness, i.e., difference of the inside and
outside diameters ID.sub.p, OD.sub.p of the plastic pipe sleeve 14;
the initial alignment provided by the manufacturing equipment; as
well as other factors affecting alignment. The angle and depth of
the respective lead-ins 34, 36, if present, is selected also as a
function of the degree of softening or "stretchability" of the
plastic pipe sleeve 14 as provided by the material selected and, if
present, the optional pre-warming provided in step C of the
process.
[0062] In step H of the invention, the longitudinal force F.sub.L
is applied as a means for driving the core 12 into the warming
device 16 and the interior of the plastic pipe sleeve 14. The
applied longitudinal force F.sub.L is sufficient for driving the
core 12 into the plastic pipe sleeve 14 while simultaneously
expanding the inside diameter ID.sub.p of the plastic pipe sleeve
14 sufficiently to receive the outside diameter OD.sub.c of the
core 12. Because the core 12 is relatively rigid and substantially
incompressible, the plastic pipe sleeve 14 expands during assembly
with the core 12, and the core 12 does not compress. The applied
longitudinal force F.sub.L necessary for installation of the
plastic pipe sleeve 14 over the core 12 is as a function of several
factors, including: the inside diameter ID.sub.p of the plastic
pipe sleeve 14 relative to the outside diameter OD.sub.c of the
core 12, whether the lubricant 18 is applied to one or both of the
core 12 and plastic pipe sleeve 14; and the "stretchability" of the
plastic pipe sleeve 14 as provided by the material selected and, if
present, the degree of softening resulting from the optional
pre-warming provided in step C of the process, as well as the
length L, of the plastic pipe sleeve 14 to be installed as
intersurface frictional forces increase with increased intersurface
area.
[0063] The longitudinal force F.sub.L is supplied by any practical
means to a second end or tail 38 of the core 12 opposite from the
first end or nose 32. By example and without limitation, an
electric, pneumatic or hydraulic other mechanical ram 40 is applied
to the foot 30 of the core 12 to supply the longitudinal force
F.sub.L. Other means for applying the longitudinal force F.sub.L
are also contemplated and are considered to be equivalent. For
example, the longitudinal force F.sub.L is alternatively applied by
gripping the tail 38 or outside wall OW.sub.p of the core 12 and
pulling or dragging the core 12 into the warming device 16 and the
plastic pipe sleeve 14. As the longitudinal force F.sub.L is
applied to the core 12, the foot 28 of the plastic pipe sleeve 14
is pushed against the stop 30 which simultaneously applies an equal
and opposite reaction force F.sub.R to the second end or foot 28 of
the plastic pipe sleeve 14 as a means for maintaining the position
of the plastic pipe sleeve 14 against slipping away under the
applied longitudinal force F.sub.L. Substantially continuous
application of the longitudinal force F.sub.L to the core 12
thereafter drives part or all of the overall length L.sub.c of the
core 12 into the plastic pipe sleeve 14.
[0064] When the lubricant 18 is present during installation,
pressure generated by the close fit of the plastic pipe sleeve 14
over the incompressible rigid core 12 results in the mouth 20 of
the plastic pipe sleeve 14 having a wiping effect against the
outside wall surface OW.sub.c of the core 12 that effective removes
or wipes away a greater portion of the lubricant 18. However, a
sufficient quantity of lubricant 18 is retained to operate as a
means for generating a thin, low friction interface between the
inside wall surface IW.sub.p of the plastic pipe sleeve 14 and the
outside wall surface OW.sub.c of the core 12 for easing the
installation.
[0065] In tests, when the assembled composite structural device 10
of the invention was sectioned crosswise to the longitudinal axis,
no lingering trace of the vegetable oil lubricant 18 was detected
between the inside wall surface IW.sub.p of the plastic pipe sleeve
14 and the outside wall surface OW.sub.c of the core 12.
[0066] FIG. 6 illustrates an alternative embodiment of the
invention wherein the ram 40 applies the longitudinal force F.sub.L
to the foot 28 of the plastic pipe sleeve 14, while the stop 30 is
positioned to apply the equal and opposite reaction force F.sub.R
to the tail 38 of the core 12. According to this optional
embodiment of the invention, the plastic pipe sleeve 14 is
pre-warmed in the warming device 16, and after attaining the
selected temperature, is driven out of the warming device 16 and
onto the core 12.
[0067] FIG. 7 illustrates a radially contracting step I of the
invention wherein the composite structural device 10 having the
selected length L.sub.p of the plastic pipe sleeve 14 installed
over the elongated cylindrical core 12 is cooled to ambient
temperature as a means for radially compressing the plastic pipe
sleeve 14 around the circumference of the outside wall OW.sub.p of
the core 12. As the heat in the plastic pipe sleeve 14 dissipates,
as indicated by the wavy heat dissipation arrows, whereby material
size "memory" of the plastic pipe sleeve 14 causes the inner
diameter ID.sub.p to return or "shrink," as indicated by the
inwardly radial compression arrows Rc, to its nominal
circumferential dimension after installation over the core 12 and
upon return to ambient temperature. As a means for facilitating and
accelerating cooling of the plastic pipe sleeve 14 and causing it
to shrink around the core 12, the composite structural device 10 is
optionally removed from the warming device 16 after assembly of the
core 12 and plastic pipe sleeve 14, unless assembly was completed
outside of the optional warming device 16, or the warming device 16
was not used. Removal from the warming device 16 also frees the
warming device 16 for a next cycle of forming the composite
structural device 10.
[0068] Shrinking of the plastic pipe sleeve 14, whether through
material memory after being stretched to admit the core 12, or
through cooling after removal from the warming device 16, causes
the plastic pipe sleeve 14 to radially contract around the outer
wall surface OW.sub.c of the core 12 forming a high compression
interface between the outer wall surface OW.sub.c of the core 12
and the inner wall surface IW.sub.p of the plastic pipe sleeve 14.
The radial compression loading at the interface is as a function of
several factors, including: a difference between the inside
diameter ID.sub.p of the plastic pipe sleeve 14 and the outside
diameter OD.sub.c of the plastic pipe sleeve 14; the size memory of
the material selected for the plastic pipe sleeve 14; and the wall
thickness of the plastic pipe sleeve 14. Even minimal radial
compression loading completely eliminates any annular separation
between the core 12 and plastic pipe sleeve 14. Furthermore, as
discussed herein, the process of the invention provides at least
minimal radial compression loading that completely eliminates any
annular separation between the core 12 and plastic pipe sleeve 14
along substantially the entire interface between the outer wall
surface OW.sub.c of the core 12 and the inner wall surface IW.sub.p
of the plastic pipe sleeve 14. Such minimal radial compression
loading also operates as a means for adhering the plastic pipe
sleeve 14 to the outer wall surface OW.sub.c of the core 12 by
generating a frictional interface over substantially the entire
intersurface area. Increasing the radial compression loading
operates to increase the intersurface frictional adhesion by
increasing the intersurface frictional forces.
[0069] Furthermore, the close or even interference fit of the core
12 and plastic pipe sleeve 14 necessitates the application of
longitudinal force F.sub.L and reactive force F.sub.R prevents
contaminants from entering the intersurface area between the outer
wall surface OW.sub.c of the core 12 and the inner wall surface
IW.sub.p of the plastic pipe sleeve 14. Therefore, the annular
joint J.sub.a developed at the interface between the core 12 and
plastic pipe sleeve 14 does not normally require protection,
neither during assembly of the composite structural device 10 nor
during circumferential contraction of the stretched plastic pipe
sleeve 14 around the outer wall surface OW.sub.c of the core 12,
whether the means for circumferential contraction is cooling or
other material memory phenomenon.
[0070] As illustrated in FIG. 7 the plastic pipe sleeve 14 does not
have to completely cover the core 12. Rather, according to one
embodiment of the invention, a portion P.sub.E at each end of the
core 12 is left exposed by the installed plastic pipe sleeve 14.
The exposed portion P.sub.E permits butt welds or other
circumferential joints J.sub.w between multiple composite pilings
10 into a longer string S of the type illustrated in FIG. 8. Thus,
according to one embodiment of the invention, the composite
structural device 10 is substantially symmetrical about a
perpendicular centerline, C.sub.L with the plastic pipe sleeve 14
exposing a substantially identical length of exposed portion
P.sub.E at both the nose 32 and tail 38 ends of the core 12.
[0071] As illustrated in FIG. 8, two or more composite devices 10
are joined by lengthwise joints J.sub.w into a longer string S.
Thereafter, a clam-shell union 42 of plastic piping material of
substantially the same or chemically similar type as the material
selected for the plastic pipe sleeve 14 is fitted over the exposed
portions P.sub.E of the joined cores 12, including the butt weld or
other lengthwise joint J.sub.w between adjacent composite pipes or
pilings 10. The clam-shell union 42 is formed of two or more
semi-cylindrical portions 44 of the selected piping material, each
of the semi-cylindrical portions 44 being sized to substantially
fill the gap G between the plastic pipe sleeves 14 of adjacent
composite pipes of pilings 10 and further to cover substantially
the entire outer surface areas of each exposed portion P.sub.E of
the joined cores 12. The clam-shell portions 44 are thereafter
thermal fusion plastic welded or chemically welded together in a
water-tight manner (hereinafter "plastic welded") by means of
lengthwise weld joints J.sub.L, to form a tube or sleeve of plastic
piping material around and completely covering the exposed portion
P.sub.E of the joined cores 12. The clam-shell portions 44 are also
plastic welded to the respective plastic pipe sleeve 14 on either
core 12 in circumferential butt weld joints J.sub.B. The lengthwise
joints J.sub.w between multiple composite devices 10 and both the
plastic lengthwise weld joints J.sub.L, and the circumferential
butt weld joints J.sub.B are accomplished in the field using
techniques generally well-known to those of skill in the relevant
art. Field welding of the cores 12 and the clam-shell union 42
permits multiple composite devices 10 to be transported to a site
of use and assembled and installed in place. Installation of the
clam-shell union 42 effectively seals the exposed portion P.sub.E
of the joined cores 12 in the gap G between the plastic pipe
sleeves 14 including the circumferential butt weld joints J.sub.B.
The clam-shell union 42 also permits the composite structural
device 10 to manufactured in standard lengths, which reduces
inventory costs.
[0072] When a non-standard or irregular length of composite
structural device 10 is required for a particular application, the
core 12 can be cut to the desired length and the plastic pipe
sleeve 14 cut and peeled off to provide the exposed portion P.sub.E
of the core 12 illustrated in FIG. 8 for joining to another core
12.
[0073] When the composite structural device 10 is not terminated
with a valve or other device, as when it is used as a piling rather
than a transmission pipe, the exposed portion P.sub.E of the core
12 is optionally sealed with an end cap 46 formed of a material
that is the same or a compatible with the plastic material of which
the plastic pipe sleeve 14 is formed. The end cap 46 is plastic
welded to the plastic pipe sleeve 14 in a circumferential butt weld
joint J.sub.B. The end cap 46 protects the exposed portion P.sub.E
of the core 12 and simultaneously protects the annular joint
J.sub.a developed at the interface between the core 12 and plastic
pipe sleeve 14, which is the weakest part of the composite
structural device 10.
[0074] FIG. 9 illustrates one embodiment of the invention wherein a
metal nose cone 48 is provided in the exposed portion P.sub.E of
the core 12 to operate as a means for protecting and sealing the
annular joint J.sub.a developed at the interface between the core
12 and plastic pipe sleeve 14 when the composite structural device
10 is driven lengthwise into the earth or other medium E. The nose
cone 48 has collar 50 from which a funnel-shaped metal skirt 52
extends. The nose collar 50 is coupled to the core 12 in the
exposed portion P.sub.E adjacent to either the nose 32 or tail 38
with the skirt "hanging" or extending toward the plastic pipe
sleeve 14. For example, a circumferential weld joint J.sub.w
secures the collar 50 to the nose 32 or tail 38 of the elongated
cylindrical core 12. According to one embodiment of the invention,
the funnel-shaped metal skirt 52 is of similar material to the core
12 and yet thin enough to be sufficiently weak to fail and collapse
while being driven lengthwise into the earth or other medium E,
whereby the failed skirt 52 collapses about the mouth 20 (or foot
28) of the plastic pipe sleeve 14 and thereby protects the annular
joint J.sub.a developed at the interface between the core 12 and
plastic pipe sleeve 14, which is the weakest part of the composite
structural device 10.
[0075] According to one embodiment of the invention, the skirt 52
is flared at an angle a of about 45 degrees from the collar 50. The
nose cone 48 is sized such that, in combination with the location
of the collar 50 relative to the plastic pipe sleeve 14, the skirt
52 is at least long enough to cover the mouth 20 (or foot 28) of
the plastic pipe sleeve 14 upon collapse. For example, when the
skirt 52 has a length L.sub.s, the collar 50 of the nose cone 48 is
positioned a distance D.sub.s from the plastic pipe sleeve 14 that
is less than or equal to (1/sqrt 2).times.L.sub.s or
0.707.times.L.sub.s.
[0076] FIG. 10 illustrates the nose cone 48 illustrated in FIG. 9
being collapsed about a portion of the exposed portion P.sub.E
adjacent to the nose 32 (or tail 38) of the core 12 and extending
over a lip portion 53 of the mouth 20 (or foot 28) of the plastic
pipe sleeve plastic pipe sleeve 14, whereby the nose cone 48
protects against entrance of foreign matter into the annular joint
J.sub.a at the interface between the core 12 and plastic pipe
sleeve 14.
[0077] FIG. 11 illustrates one embodiment of the invention that is
useful for the composite structural device 10 being used as a
piling. Accordingly, a quantity of supplemental rub strips 54 are
coupled to the outer wall surface OW.sub.p, of the plastic pipe
sleeve 14 as a means for protecting the integrity of the plastic
pipe sleeve 14 in high wear applications. For example, when used as
a piling in a marina, heavy metal retaining hoops of a type
well-known in the industry may be used to circle the composite
structural device 10 for retaining a dock. In such an application,
the retaining hoop and dock may both rub against the plastic pipe
sleeve 14 of the composite structural device 10 as a function of
fluctuating water levels, and in particular as a function of tidal
motion. The supplemental rub strips 54 are slats formed of a
material that is the same or a compatible with the plastic material
of which the plastic pipe sleeve 14 is formed. The supplemental rub
strips 54 are plastic welded to the plastic pipe sleeve 14 in a
circumferential pattern in longitudinal alignment with the
longitudinal axis A.sub.c of the core 12. Because the supplemental
rub strips 54 are provided on the outer wall surface OW.sub.p of
the plastic pipe sleeve 14, they forcibly space the retaining hoop
and dock away from the plastic pipe sleeve 14. The supplemental rub
strips 54 wear rather than the plastic pipe sleeve 14 so that the
core 12 remains protected. When the supplemental rub strips 54
sufficiently worn to be in danger of exposing the plastic pipe
sleeve 14 to wear, the supplemental rub strips 54 can be replaced,
or additional supplemental rub strips 54 can be plastic welded over
the worn strips 54.
[0078] FIG. 12 illustrates another embodiment of the invention that
is useful for the composite structural device 10 being used as a
piling. Accordingly, a traveler 56 is provided over the outer wall
surface OW.sub.p of the plastic pipe sleeve 14 as a means for
protecting the integrity of the plastic pipe sleeve 14 in high wear
applications, such as the marina application described herein.
Accordingly, the traveler 56 is a length L.sub.T of plastic pipe
having an inside diameter ID.sub.T that is sufficiently larger than
the outside diameter OD.sub.p of the plastic pipe sleeve 14 to
permit the traveler 56 to slide along the length L.sub.p of the
plastic pipe sleeve 14 without interference. Additionally, a stop
58 is optionally coupled to the outer wall surface OW.sub.p of the
plastic pipe sleeve 14 as a means for maintaining the traveler 56
within a selected range or zone Z. The supplemental rub strips 54
illustrated in FIG. 11 is optionally provided as the stop 58,
wherein the strips 54 are sufficiently thick to interfere with
travel of the traveler 56. Alternatively, the stop 58 is provided
as a ring sized to fit closely with the outer wall surface OW.sub.p
of the plastic pipe sleeve 14 and thick enough to simultaneously to
interfere with travel of the traveler 56. For example, the stop 58
is a short section of thick-walled plastic pipe formed of a
material that is the same or a compatible with the plastic material
of which the plastic pipe sleeve 14 is formed and is plastic welded
in a position that is selected to maintain the traveler 56 in the
selected range or zone Z. When the traveler 56 is formed of a
plastic of sufficiently low density to float in water, it will
float up and down with fluctuation of the water. However, the user
may find it useful to add a second stop 58 of the type described
herein to operate as a means for limiting the overall motion of the
traveler 56 to a controlled zone Z, which also interferes with
unusual water levels, vandals or other phenomenon removing the
traveler 56 from the composite structural device 10.
[0079] FIG. 12 also illustrates an alternative embodiment of the
invention wherein the core 12 is completely enclosed and sealed
within the plastic pipe sleeve 14 and a pair of end cap plates 60
formed of a material that is the same or a compatible with the
plastic material of which the plastic pipe sleeve 14 is formed. As
illustrated at the upper portion of FIG. 12, the length L.sub.p of
the plastic pipe sleeve 14 is extended beyond the tail 38, i.e.,
the entire length L.sub.c of the core 12, by the thickness T of the
cap plates 60. The cap plates 60 plastic sized to fit within the
inside diameter ID.sub.p of the plastic pipe sleeve 14 and are
welded thereto in a circumferential butt weld joint J.sub.C.
[0080] Alternatively, as illustrated at the lower portion of FIG.
12, the length L.sub.p of the plastic pipe sleeve 14 is extended
over the entire length L.sub.c of the core 12, but does not extend
beyond the nose 32 of the core 12. The cap plates 60 are sized
substantially the same as the outside diameter OD.sub.p of the
plastic pipe sleeve 14 and are welded thereto using the
circumferential butt weld joint J.sub.C. The cap plates 60
according to one or both of the alternative embodiments are welded
to the plastic pipe sleeve 14 and, in combination with the plastic
pipe sleeve 14, completely encapsulate the core 12.
[0081] While the preferred embodiment of the invention has been
illustrated and described, it will be appreciated that various
changes can be made therein without departing from the spirit and
scope of the invention. For example, materials may be substituted
for the different components of the flexible support apparatus of
the invention without departing from the spirit and scope of the
invention. In another example, the inventor has actually practiced
the process of the invention by nonuniformly pre-warming the
plastic pipe sleeve 14 using a propane torch, installing the core
12 by applying the nose 32 of a pipe-type core 12 to the sleeve
mouth 20, applied the longitudinal force F.sub.L by installing the
pipe-type core 12 over a fork of a motorized fork-lift device and
driving the fork-lift device toward the plastic pipe sleeve 14 with
the sleeve foot pressed against a building wall as the stop 30 for
applying the reactive force F.sub.R against which the longitudinal
installation force F.sub.L was operated, and allowed the composite
structural device 10 to cool in room ambient atmosphere. Therefore,
the inventor makes the following claims.
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